Paginate ebs_snapshot_count check

[kedoodle]

This PR fixes a memory usage issue whereby quota checks make a single boto3 call, even when supposedly paginating. Symptoms described in this comment on #31.

• Uses the existing paginator to count the ebs_snapshot_count quota
• Sets a default pagination page size (otherwise the paginator just gets all resources in my testing of describe_snapshots)
• Fixes up an error log message

See memory usage spikes to ~800 MiB on 1.10.0 and is fairly stable at ~50 MiB on this branch.

Before:

• Locally

  $ time aws-quota-checker check ebs_snapshot_count
  
  AWS profile: default | AWS region: ap-southeast-2 | Active checks: ebs_snapshot_count
  EBS Snapshots per Region [xxx/ap-southeast-2]: 34896/100000 ✓
  aws-quota-checker check ebs_snapshot_count  12.72s user 2.32s system 3% cpu 7:27.41 total

• In cluster (~3 minutes):

  AWS profile: default | AWS region: ap-southeast-2 | Active checks: 
  cf_stack_count,ebs_snapshot_count,rds_instances,s3_bucket_count
  ...
  07-Jan-22 06:10:21 [INFO] aws_quota.prometheus - refreshing current values
  07-Jan-22 06:13:39 [INFO] aws_quota.prometheus - current values refreshed

After:

• Locally:

  $ time aws-quota-checker check ebs_snapshot_count
  
  AWS profile: default | AWS region: ap-southeast-2 | Active checks: ebs_snapshot_count
  EBS Snapshots per Region [xxx/ap-southeast-2]: 34899/100000 ✓
  aws-quota-checker check ebs_snapshot_count  12.33s user 1.36s system 16% cpu 1:25.01 total

• In cluster (~1 minute):

  AWS profile: default | AWS region: ap-southeast-2 | Active checks: 
  cf_stack_count,ebs_snapshot_count,rds_instances,s3_bucket_count
  ...
  07-Jan-22 08:47:46 [INFO] aws_quota.prometheus - refreshing current values
  07-Jan-22 08:48:55 [INFO] aws_quota.prometheus - current values refreshed

[brennerm]

Thanks for the contribution, looking good! :+1:

[brennerm]

Change has been released in version 1.11.0.